dma: contiguous: Turn heap registration logic around

The CMA heap instantiation was initially developed by having the
contiguous DMA code call into the CMA heap to create a new instance
every time a reserved memory area is probed.

Turning the CMA heap into a module would create a dependency of the
kernel on a module, which doesn't work.

Let's turn the logic around and do the opposite: store all the reserved
memory CMA regions into the contiguous DMA code, and provide an iterator
for the heap to use when it probes.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-1-e18fda504419@kernel.org

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index bd3370b9a3f6d4e18885a1d0e8ba3f659b85ef47..33cac626da1198e3c4a1cdcd562223c1924b6ceb 100644 (file)
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -14,7 +14,6 @@
 
 #include <linux/cma.h>
 #include <linux/dma-buf.h>
-#include <linux/dma-buf/heaps/cma.h>
 #include <linux/dma-heap.h>
 #include <linux/dma-map-ops.h>
 #include <linux/err.h>
@@ -30,19 +29,6 @@
 
 #define DEFAULT_CMA_NAME "default_cma_region"
 
-static struct cma *dma_areas[MAX_CMA_AREAS] __initdata;
-static unsigned int dma_areas_num __initdata;
-
-int __init dma_heap_cma_register_heap(struct cma *cma)
-{
-       if (dma_areas_num >= ARRAY_SIZE(dma_areas))
-               return -EINVAL;
-
-       dma_areas[dma_areas_num++] = cma;
-
-       return 0;
-}
-
 struct cma_heap {
        struct dma_heap *heap;
        struct cma *cma;
@@ -414,6 +400,7 @@ static int __init __add_cma_heap(struct cma *cma, const char *name)
 static int __init add_cma_heaps(void)
 {
        struct cma *default_cma = dev_get_cma_area(NULL);
+       struct cma *cma;
        unsigned int i;
        int ret;
 
@@ -423,9 +410,7 @@ static int __init add_cma_heaps(void)
                        return ret;
        }
 
-       for (i = 0; i < dma_areas_num; i++) {
-               struct cma *cma = dma_areas[i];
-
+       for (i = 0; (cma = dma_contiguous_get_area_by_idx(i)) != NULL; i++) {
                ret = __add_cma_heap(cma, cma_get_name(cma));
                if (ret) {
                        pr_warn("Failed to add CMA heap %s", cma_get_name(cma));

diff --git a/include/linux/dma-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h
deleted file mode 100644 (file)
index e751479..0000000
--- a/include/linux/dma-buf/heaps/cma.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef DMA_BUF_HEAP_CMA_H_
-#define DMA_BUF_HEAP_CMA_H_
-
-struct cma;
-
-#ifdef CONFIG_DMABUF_HEAPS_CMA
-int dma_heap_cma_register_heap(struct cma *cma);
-#else
-static inline int dma_heap_cma_register_heap(struct cma *cma)
-{
-       return 0;
-}
-#endif // CONFIG_DMABUF_HEAPS_CMA
-
-#endif // DMA_BUF_HEAP_CMA_H_

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 60b63756df821d839436618f1fca2bfa3eabe075..c4c93c72ff6ff3ff5c59b7161970805422e9dccb 100644 (file)
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -99,6 +99,7 @@ static inline struct cma *dev_get_cma_area(struct device *dev)
                return dev->cma_area;
        return dma_contiguous_default_area;
 }
+struct cma *dma_contiguous_get_area_by_idx(unsigned int idx);
 
 void dma_contiguous_reserve(phys_addr_t addr_limit);
 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
@@ -117,6 +118,10 @@ static inline struct cma *dev_get_cma_area(struct device *dev)
 {
        return NULL;
 }
+static inline struct cma *dma_contiguous_get_area_by_idx(unsigned int idx)
+{
+       return NULL;
+}
 static inline void dma_contiguous_reserve(phys_addr_t limit)
 {
 }

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index c56004d314dc2e436cddf3b20a4ee6ce8178bee4..afa9fd31304051d200cd4396dec26dd50becc375 100644 (file)
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -42,7 +42,6 @@
 #include <linux/memblock.h>
 #include <linux/err.h>
 #include <linux/sizes.h>
-#include <linux/dma-buf/heaps/cma.h>
 #include <linux/dma-map-ops.h>
 #include <linux/cma.h>
 #include <linux/nospec.h>
@@ -53,6 +52,37 @@
 #define CMA_SIZE_MBYTES 0
 #endif
 
+static struct cma *dma_contiguous_areas[MAX_CMA_AREAS];
+static unsigned int dma_contiguous_areas_num;
+
+static int dma_contiguous_insert_area(struct cma *cma)
+{
+       if (dma_contiguous_areas_num >= ARRAY_SIZE(dma_contiguous_areas))
+               return -EINVAL;
+
+       dma_contiguous_areas[dma_contiguous_areas_num++] = cma;
+
+       return 0;
+}
+
+/**
+ * dma_contiguous_get_area_by_idx() - Get contiguous area at given index
+ * @idx: index of the area we query
+ *
+ * Queries for the contiguous area located at index @idx.
+ *
+ * Returns:
+ * A pointer to the requested contiguous area, or NULL otherwise.
+ */
+struct cma *dma_contiguous_get_area_by_idx(unsigned int idx)
+{
+       if (idx >= dma_contiguous_areas_num)
+               return NULL;
+
+       return dma_contiguous_areas[idx];
+}
+EXPORT_SYMBOL_GPL(dma_contiguous_get_area_by_idx);
+
 struct cma *dma_contiguous_default_area;
 
 /*
@@ -264,9 +294,24 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
                if (ret)
                        return;
 
-               ret = dma_heap_cma_register_heap(dma_contiguous_default_area);
+               /*
+                * We need to insert the new area in our list to avoid
+                * any inconsistencies between having the default area
+                * listed in the DT or not.
+                *
+                * The DT case is handled by rmem_cma_setup() and will
+                * always insert all its areas in our list. However, if
+                * it didn't run (because OF_RESERVED_MEM isn't set, or
+                * there's no DT region specified), then we don't have a
+                * default area yet, and no area in our list.
+                *
+                * This block creates the default area in such a case,
+                * but we also need to insert it in our list to avoid
+                * having a default area but an empty list.
+                */
+               ret = dma_contiguous_insert_area(dma_contiguous_default_area);
                if (ret)
-                       pr_warn("Couldn't register default CMA heap.");
+                       pr_warn("Couldn't queue default CMA region for heap creation.");
        }
 }
 
@@ -506,9 +551,9 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
        pr_info("Reserved memory: created CMA memory pool at %pa, size %ld MiB\n",
                &rmem->base, (unsigned long)rmem->size / SZ_1M);
 
-       err = dma_heap_cma_register_heap(cma);
+       err = dma_contiguous_insert_area(cma);
        if (err)
-               pr_warn("Couldn't register CMA heap.");
+               pr_warn("Couldn't store CMA reserved area.");
 
        return 0;
 }